It is held that march music may induce soldiers marching in unison into trance states. They bond together as a unit engendered by the rigors of training, the ties of comradeship and the chain of command. The detractor may hold that they entrain as automaton. Instruments, especially snare drums, entone a monotonous ostinato at the pace of march and heartbeat. High-pitched fifes, flutes and bagpipes used for their piercing effect, play the melody.